SNII event

Beryllium and boron evolve in the same way as iron, showing that SNII events are responsible for these three elements. 

SNII events alone explain the observed solar abundance distribution between oxygen and chromium. This can be taken as a major theoretical achievement. Complementary sources of hydrogen, helium, lithium, beryllium, boron, carbon and nitrogen are required, and these have been identified. They are the Big Bang, cosmic rays and intermediate-mass stars. Around iron and a little beyond, we must invoke a contribution from type la supernovas (Pig. 8.5). These must be included to reproduce the evolution of iron abundances, a fact which suggests... 

We conclude that the process responsible for the production of r-type isotopes beyond barium has operated in the same way since the origin of the Galaxy. The process is therefore unique. There is little risk of error in suggesting that it is related to SNII events. We may then define the conditions of neutron irradiation and thermodynamic parameters relevant to this nucleosynthesis, without necessarily being able to establish the detailed mechanism. 

The endpoint in the evolution of stars with more than 8 solar masses is a type II supernova. One should not confuse novae with supemovae and even the two types (i.e., type I and type II) of supemovae are quite different. It will become evident in the following that the sites of these explosive events are only loosely related, despite the similarity in the name. There is a major difference in the underlying mechanism between type I (SN I) and type II supernovae (SNII). The confusing choice of names is, once again, historical. Astronomy is guided by observations... 

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